Many electrical and electronic devices (such as electronic connectors and switches) must exhibit very high reliability. For example, switches that are used to trigger the release of automobile air bags often are required to remain operational, despite non-use, over extended periods of time. In another example, electronic connectors used in high-speed data transmission at conditions which include relatively low-voltage and low-current generally must operate without failure in order to prevent interruptions in data transmission. However, electrically conductive interconnectors within such devices typically are formed of metals which can corrode after wear at surfaces exposed to the atmosphere. Corrosion at surfaces where contact is made often significantly reduces the lifetime reliability of electronic devices which include such interconnectors.
One attempt to improve the reliability of electronic devices is to bond a relatively non-corrosive electrically conductive contact layer to electrically conductive interconnectors at surfaces where contact, such as during switch closure. Contact layers are typically formed of a noble metal or an alloy thereof. However, noble metals are relatively expensive. As a result, contact layers generally are fabricated to be as thin as possible without causing failure under expected use-conditions. Also, noble metals are relatively soft and, therefore, can wear away during repeated operation of electronic devices. The relatively corrosive metal beneath the contact layers can thereby be exposed to the atmosphere, ultimately causing failure of these electronic devices.
Liquid lubricants have been applied to surfaces of contact layers in an attempt to reduce wear. However, many liquid lubricants are considered hazardous, especially during their application, which often involves use of volatile chlorinated hydrocarbon dispersants. In addition, liquid lubricants can become unevenly distributed on contact layer surfaces and can evaporate or creep away, thereby causing portions of the contact layers to be exposed to conditions which can result in excessive wear and consequent premature failure. Additionally, liquid phase lubricants typically attract dust and abrasive particles from the atmosphere which accelerate wear and corrosion in the contact area, thereby resulting in significantly reduced contact reliability. Also, many liquid lubricants are relatively poor electrical conductors, thereby causing relatively high electrical resistance across closed contact surfaces and possible failure of electronic devices which include such contact surfaces.
Solid-phase lubricants have also been applied to the surfaces of contact layers in an attempt to reduce wear. Commonly used solid-phase lubricants include graphite, molybdenum disulfide and various plastics. Typically, these have been applied by air-spraying, sputtering and ion plating. However, the wear durability of these surface coatings is limited because the motion of sliding contacts tends to plow away the solid-phase lubricant from the wear track, thereby leaving a pile-up of lubricant and wear-debris at the ends of the wear track. Also, solid-phase lubricants typically are poor electrical conductors, thereby causing high electrical resistance across contact surfaces which come to rest upon a particle of the solid-phase lubricant.
Thus, a need exists for an electrically conductive composition and an electrically conductive interconnector which overcome or minimize the above-mentioned problems.